1. Field of the Invention
The present invention relates to a semiconductor laminating structure suitable for use with a semiconductor light emitting device or the like, for example. More specifically, the present invention relates to a semiconductor light emitting device, a field-effect transistor or the like having a semiconductor laminating structure which includes a semiconductor layer made of a GaN system chemical compound containing elements of N and at least one of Al, B, Ga and In.
2. Background of the Invention
A GaN system III-V family crystal allows its band gap energy to be changed in a range of 1.95 eV to 6.2 eV depending on its composition. Thus, the crystal draws an attention as a luminescent material capable of emitting light having each wavelengths over a wide range from red to ultraviolet.
Particularly, since a light emission diode LED of a high luminance using a material of GaN is recently realized, research over such a light emission diode LED has been done prosperously.
At present, as a substrate for growing thereon a GaN system material, a sapphire crystal (.alpha.-Al.sub.2 O.sub.3) is generally and widely utilized. However, there is such a large lattice mismatch as 16.1% between a GaN crystal and the sapphire crystal. Further, both of them have thermal expansion coefficients different from each other. Therefore, the sapphire crystal is not necessarily best suited substrate. The large lattice mismatch causes increase in dislocation density and a non-radiative center in the GaN crystal grown on the substrate and decrease in life of radiation recombination. Thus, the lattice mismatch may cause considerable influence on characteristics of various elements such as a laser diode, in particular, which requires current injection at high energy and so on.
In consequence, a 6H-SiC substrate, a Si substrate, a GaAs substrate, a ZnO substrate, a MgO substrate, a MgAl.sub.2 O.sub.4 substrate and so on are discussed as a substrate capable of replacing for the sapphire substrate which has been utilized for laminating thereon a semiconductor laminating structure made of a GaN system III-V family chemical compound. However, each of the materials has an advantage and a disadvantage in a state of crystal, and there has been proposed no excellent substrate yet that can replace for the sapphire substrate.